(1) An external hard disk drive or optical disc drive that plugs into the USB port. See portable hard drive.
(2) A solid state storage module that plugs into the computer's USB port. Using flash memory chips that hold up to one terabyte of data, the solid state USB drive emulates a hard disk. USB drives are extremely popular for backup as well as data transfer from one machine to another. They can also hold an operating system and be used to boot the computer (see bootable disk). Their ever-increasing storage capacities have mostly obsoleted writable CDs and DVDs. See sneakernet. Known By Many Names Debuting at the turn of the century, a USB drive is also called a "flash drive" as well as many other monikers. Any combination of the words "USB," "flash," "key," "drive," "jump" and "stick" are used (see USB drive names). Transfer Speed USB drive vendors use the data transfer ratings of CD-ROMs, where each "x" equals 150KB per second. For example, a 90x drive is 13.5MB/sec (90 x 150). See CD-ROM drives and solid state.